In anesthesia or in intensive care, the condition of a patient is often monitored e.g. by analyzing the air exhaled by a patient. Special attention is paid to the carbon dioxide content exhaled by a patient. The content of anesthetic gases is also often monitored. Therefore, a small portion of the exhalation air is delivered to a analyzing unit. This sample often carries along to the analyzing unit some water vapour, which condenses into droplets, and also some dust, mucus and blood. Such components carried along with the sample have a detrimental effect on the analyzing unit and measuring result. This is why the liquid components are often removed and collected from a gas sample upstream of the actual analyzing unit. A water separator and a method developed for this purpose are disclosed in U.S. Pat. Nos. 4,304,578 and 4,382,806. In order to separate liquid components, a gas sample is delivered into a rather small chamber, wherein the flow divides into two components.
The main flow keeps running from the top section of this chamber to an analyzing unit while the minor side flow is carried from the bottom section of the chamber out of reach of the analyzing unit, usually by way of a water receiver. The purpose is to condense the liquid, definitely vapourized by this time, condensate on the chamber walls and to carry on its passage down to a water receiver together with the rest of the liquid secretion. However these solutions are not totally sufficient, since some of the liquid components may still find access to an analyzing unit along with the main flow.
According to later solution described in U.S. Pat. No. 4,886,528 a chamber, wherein a liquid component is separated from a gas flow, is divided into two sections by means of a gas permeable and liquid-impermeable material. Thus, a sample picked up from the exhalation air of a patient is delivered into the first chamber of a water separator, from which the liquid component along with a minor amount of gas is sucked away, usually by way of a water receiver. Most of the gas flow received in the first chamber is sucked through the liquid-impermeable material into the second chamber and further to an analyzing unit. This material prevents effectively the passage of liquid to the analyzing unit.
The last described solution works well as long as just a moderate amount of liquid secretions are entrapped in the exhalation air of a patient. If, for some reason, however, a patient secretes e.g. mucus more than in a normal case, the liquid-impermeable material installed in the chamber will be choked up rather quickly, thus preventing the passage of gas samples to the analyzing unit.